A computer can use a reminder to inform a user that a task needs to be performed or an event is going to happen. For example, a computer can store a to-do list for a user. The to-do list can include a list of one or more tasks. Each task can be associated with a scheduled due date. As the due date of a task approaches, the computer can provide a reminder to the user, for example, by presenting an alert dialog box. In some implementations, the to-do list can be managed by a calendar application program. The calendar application program can allow the user, after logging in, to create or modify the to-do list, and to view the reminders.